Remote Canister stove Recommendations

Jim – I would expect to see the same initial flame size with inverted and non-inverted canster when the valve is fully open. Initial flame size only because the evaporative cooling in the non-inverted canister will quickly reduce the pressure within. When the valve is partially open then the degree of restriction is different for gas than for liquid so I would expect this to give a different flame size. cheers.

Interesting. Thank you for that, Stuart.

So they start out at the same flame size, but as the internal pressure drops in upright mode due to evaporative cooling, the internal canister pressure will fall and the flame size will in turn decrease. In inverted mode, their isn’t the same degreee of evaporative cooling, therefore the internal canister pressure doesn’t fall as much, and flame size stays larger. All this with the valve open fully.

What I’ve observed is that flame size makes a sudden and dramatic increase when I invert a canister, but I don’t know that I’ve ever inverted a canister with the valve fully open (standard advice is to turn the stove down precisely because flame size does tend to surge when the canister is inverted).

And the reason that the flame size increases when the canister is inverted but the valve is not fully open lies in the fact that liquid fuel exists at the valve whereas gaseous fuel exists at the jet, yes? Can you say more about the particulars? I understand that more mass (a greater number of molecules) will travel through the valve since the fuel flow here will be liquid whereas less mass will travel through the jet since the fuel there will be in gaseous form, but I don’t quite understand the mechanism whereby the flame size increases upon inversion. Is it simply one of impedence? That is, is it harder for the liquid to flow back through the valve than it is for gas to exit the jet and therefore effective pressure is created in the direction of the jet? I’m just having trouble visualizing what’s going on here.

I’m sure the fact that it was a friend’s birthday last night and that the vodka was flowing freely has nothing to do with my current lack of comprehension. ;) Please pardon my slowness.

HJ
Adventures In Stoving

> I was trying hard not to over-complicate my original explanation…
Stuart, Stuart – we THRIVE on complications!
:-)

Cheers
PS: Al wire might work even better?

Hi Jim

> > So there should be very little difference in peak power between inverted and
> > non-inverted canister operation, as long as the canister is warm enough.
> You're saying that all I need to do is just open up the valve further, and I'll get
> the same kind of high output?

I should have added emphasis to the phrase 'peak power'. But since you probably never run at absolute peak power, you may not have seen this.

Yes, when you invert a canister under typical conditions you will get a change in flame. That's because the mass flow rate through the needle valve changed when it switched from gas flow to liquid flow. Remember the 250:1 expansion from liquid to gas!

If the hose presents a significant obstruction to the flow, then you may also get a difference due to that. Obviously you can get more mass down a partially blocked hose in liquid form than in gas form. Yeah, tricky.

That SOTO video shows a flame decreasing as the canister cools. Any walker would simply open the valve a little more when this happens. Dead simple. The SOTO regulator does that for you. Well, big deal of course.

Cheers

I still don’t understand the interplay between the internal pressure within the canister, the pressure from expansion in the generator, and the higher mass flow through the valve. Perhaps a decent night’s sleep will allow me to conceptualize it, but if anyone has a good illustrative analogy, I am all ears.

HJ
Adventures In Stoving

Obviously you want vapor going out the jet, not liquid, whether the canister is upright or inverted. The valve though will see liquid when the canister is inverted.

I played around with a JetBoil Helios in the snow last weekend. It seems that the stove output increased quite a bit when inverting the canister, but that was at low valve openings. I presume that if we were at full throttle then the jet would be the limiting factor and the flow wouldn't change when inverting.

Jim W.

Obviously you want vapor going out the jet, not liquid, whether the canister is upright or inverted. The valve though will see liquid when the canister is inverted.

I played around with a JetBoil Helios in the snow last weekend. It seems that the stove output increased quite a bit when inverting the canister, but that was at low valve openings. I presume that if we were at full throttle then the jet would be the limiting factor and the flow wouldn’t change when inverting.

Jim W.
[emphasis added]

Jim,

I think you’ve hit on something there. I sat down with a friend of mine who is a mechanical engineer. Here’s a synopsis of what he told me.

There will be a drop in pressure at the valve and at the jet. Generally, the pressure drop is less when the fuel is in liquid form (unless the liquid is highly viscous, as in tar). When the fuel is in liquid form (as in inverted canister operation), there will be less of a drop in pressure at the valve. Therefore, for a given pressure in the canister, the pressure in the fuel hose is greater if the fuel is liquid. In general, greater pressure equates to greater flow at the jet. Of course there is an upper limit at which increasing pressure does little to increase the flow, which, just as you suggest is due to the jet size. I assume this is what Roger was refering to in his remarks about peak power being about the same regardless of the orientation of the canister.

Before I talked to my friend, I understood that there was more mass moving through the valve when the fuel was in liquid form. But wouldn’t high pressure created by the expansion of the fuel from liquid form to gaseous form inside the pre-heat loop create an impediment to that higher mass flow? Indeed it would, for pressure flows from high to low. What I lacked was the understanding that the pressure in the fuel hose will be higher with liquid fuel. That higher pressure causes greater fuel flow through the system which results in a flame surge (markedly) at the burner, limited by the jet size.

At low canister pressures, one might get an increase in flame size when one inverts the canister even with the valve fully open.

HJ
Adventures In Stoving